Such a device is known, especially for gas reservoirs under pressure that could be destroyed by an excess pressure. The aforementioned given force is typically obtained by a calibrated spring.
The valve device of the present invention is intended for a system for carrying out chemical depositions from the vapour phase, especially to an epitaxy reactor. In this case, the space of the reactor is not normally subjected to high pressures, but specific problems arise. Highly toxic gases are used therein, which involves the necessity of providing a washing and purification at the outlet and solid deposits are formed therein. These deposits are susceptible to clogging the outlet gas nozzles and consequently producing an excess pressure in the reactor: such excess pressures must be absolutely avoided, even if they are very low (the limit not to be exceeded is about 0.1 bar) and even if they are of short duration. Since the gas flow rate in the reactor is about 60 to 80 liters/min and the internal volume of the reactor is about one liter, an excess pressure of 0.1 bar can be attained in one tenth of a second if the gas outlet is clogged.
A protection device for such an apparatus must therefore have the following properties:
It operates in a reliable and reproducible manner, even for low excess pressures. PA1 Its action is very rapid. PA1 Its switching-on pressure is adjustable. PA1 The fact that the device has acted can be readily detected. PA1 Its tightness is perfect and controllable.